If your Windows 7 always get stuck on the Welcome Screen or if you cannot proceed to the login screen or if you have this "Black Screen of Death", Go to Safe Mode>press Start and type "msconfig"> Hit Enter> Press Services tab> Check Hide all> click Disable all> Restart if prompted.

After restarting, Press Start again> type "msconfig" again without quotations> click Services tab> enable one or two start up services then reboot again. Continue this process until you find out what service is causing the problem.